The objective of this research is to determine the dependence of the biological action of ionizing radiation on the spatial distribution of energy absorption in mammalian cells. This relation is essential to an understanding of radiobiology and for its quantitative expression in dose-effect curves, relative biological effectiveness and their modification by physiological and biochemical agents. A systematic variation of the radiation pattern is achieved in irradiation by energetic ions at various separations of the order of tens of nanometers and subsidiary use of X-rays producing electrons of ranges down to a few nanometers. The biological effects investigated are cell killing, chromosome aberrations, mutations and oncological transformations. The cells are of rodent and human origin. The modifying factors include anoxia and both enhancers (bromodeoxyuridine) and reducers (cysteamine) of radiation effects. The detailed track structure of the radiation is calculated and the theoretical analysis provides the functional relation between the distance of energy deposits and the probability of biological effects.